loose chain gaurd or rock stuck in there?

 

i took the chain guide off and cleaned it, no big rocks just some dirt/mud and grease. doesnt look like the metal part of the guide is anywhere near touching the sprocket and i wouldnt think that the hard plastic could put a groove in the metal sprocket

 

i took some pics w/ my phone but cant figure out how to get them off of it yet

 

It is possible that this is from a rock a long time ago, get the back tire off the ground and spin the tire and see what happens.

 

think its just genral chain whare got same problem on my yz 125!! it was gold now got big grooves round outside of sprocket